This invention relates to a comparator circuit comprising a comparator which includes a first and a second supply terminal for connecting a supply voltage to these terminals, a first input terminal for connecting a reference voltage, and a second input terminal connected via an attenuation means to a signal terminal for connection to an input voltage. A comparator circuit of this type is of general knowledge and is used for a great variety of applications. The input voltage is compared with the reference voltage and the comparator signals when the input voltage exceeds the reference voltage. The reference voltage has a value which lies in the supply voltage range of the comparator. For measuring input voltages which are large relative to the comparator reference and supply voltages, an attenuator is generally used to bring the input voltage within the range determined by the supply voltage. In lieu of the attenuation means, a resistance divider may be used which has a large series resistance between the signal terminal and the second input terminal and, as required, a further resistance between the second input terminal and the second supply terminal. In that case there is a linear relationship between the input voltage and the attenuated voltage on the second input terminal of the comparator. In many cases the linear relationship is not even required. In that case the attenuation means may, in known fashion, consist of a series resistance between the signal terminal and the second input terminal and clamping means between the second input terminal and the second supply terminal so as to limit the signal. A disadvantage of these known attenuators is the series resistance. This has to be a large value which is objectionable especially in integrated circuits. Another known non-linear attenuation is obtained by means of a diode whose cathode is connected to the signal terminal and whose anode is connected to the second input terminal of the comparator and also, by means of a series resistance, to the reference voltage source. The diode is blocked to high signal voltages and rendered conductive in the case of signal voltages smaller than or equal to the reference voltage. A disadvantage of this known attenuator is the voltage drop across the diode, which is undesirable in the case of relatively small input voltages.